The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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COMPARISON OF VIBRATION, INFRARED AND COMBINED INFRARED WITH VIBRATION WELDING OF PMMA TO ABS
Vibration welding is one of the most popular techniques for joining thermoplastics. For vibration welding, irregular flash formation results in poor aesthetics while infrared (IR) welding has more desirable flash aesthetics. In this work, we compare vibration, IR, and combined IR with vibration welding of PMMA to ABS. Vibration welding had the shortest cycle time with strong joints of 89% of the bulk strength of the weaker ABS. IR welding had much longer cycle times, nicer flash aesthetics but weaker welds with maximum joint strength that was 71% of the bulk strength of ABS. Combined IR with vibration welding had intermediate cycle times, with the same joint strengths (91% of bulk strength of ABS) as just vibration welding and with nearly the same flash aesthetics as just IR welding.
EFFECTS OF INFRARED PREHEATING ON ANGULAR DISTORTION OF VIBRATION WELDED TPO
Thermoplastic polyolefins (TPO) are frequently used in automotive applications. Vibration welding is often used to join parts together, resulting in joints that are not as strong as the bulk and in angular distortion in Tee-joints. In this study, we evaluated the effects of infrared (IR) preheating of the web plate prior to vibration welding on weld strength and angular distortion of Tee-joints. It was found that angular distortion could be significantly reduced by as much as 50% for IR preheating times of 10 or 15 sec. Strength on the other hand increased for lower IR preheating times of 8 and 10 sec. compared to vibration welding only.
DESIGN OF EXPERIMENTS ON THE EFFECTS OF PROCESSING PARAMETERS FOR LEUCO DYES
The purpose of this experiment is to determine what processing variables can alter the initial color of leuco dyes. A Design of Experiments (DOE) was performed in order to test what effect the different processing parameters had on the samples initially. The samples were made using an impact disc mold and an injection molding machine with a copolymer polypropylene base material. After the parts sufficiently cooled a reading was taken to determine the color of the impact discs. At the conclusion of the experiment it was found that barrel temperature had the greatest impact on the initial color of the part.
THE EFFECTS OF THE PROCESSING PARAMETERS OF INJECTION FOAM MOLDING ON GLASS-FIBER REINFORCED POLYPROPYLENE
Automotive manufacturers have been actively searching for lighter and stronger materials to improve fuel efficiency and to possibly reduce material costs. Glass-fiber reinforced polymer parts have been replacing some of their metal counterparts for the last few decades for these purposes. Efforts continue to focus on further reducing weight and cost without a major compromise to the required properties of the parts. It is well known that foaming technology can provide a significant weight reduction, but their effects on glass-fiber composites have not been fully explored yet. In this context, this research has utilized injection foam molding technology to develop a glass-fiber reinforced polypropylene and has analyzed the effects of its processing parameters on a wide range of properties of the structures produced.
THE EFFECT OF CASTING CONDITION ON HEAT SEAL PROPERTY OF HIGH DENSITY POLYETHYLENE FILM
Film cast condition in T-die extruding processing affects molecular structure development. Relationship between the molecular structure development and the external form, width and thickness in T-die extruding of high-density polyethylene (HDPE) was studied. The film width and thickness distribution changed proportional to cast conditions, chilled roll speed, chilled roll surface temperature, mass throughput rate. On the other hand, molecular orientation, crystalline orientation and other factors did not develop proportionally to the cast conditions. The cast conditions are important factors to affect molecular structure. Molecular structure is also an important for heat seal properties. Heat seal strength changed depending on cast conditions. In low chilled roll speed heat seal strength was low. The failure mode was peeling. In high chilled roll speed heat seal strength was high. The failure mode was changed to tearing. To discuss major factor to decide heat seal properties, the effects of molecular orientation and film thickness were studied. The film thickness was not major factor to decide heat seal properties in this study. Both peeling and tearing were observed for film thickness from 10 to 30 ?¬m. However film thickness is also important factor to affect the heat conductive rate directly. Crystallinity was important factor to affect heat seal properties. Molecular orientation was also a major factor to decide heat seal properties in this study. The failure mode of peel test was changed drastically at 0.025 birefringence. Molecular orientation was an important factor to decide heat seal properties as well as crystallinity.
EPOXY THERMOSET TOUGHENED WITH AMPHIPHILIC BLOCK COPOLYMERS
In order to take full advantage of the properties of epoxy thermosets it is sometimes necessary to improve their toughness. Usually this is done by adding toughening agents. Typical toughening agents such as thermoplastics or elastomers can do a good job of improving toughness but often this improvement comes at the expense of desirable mechanical properties such as modulus, thermal properties such as the glass transition temperature (Tg) and/or ease of processibility of the uncured formulation (undesirable changes in viscosity). This paper focuses on the use of an amphiphilic block copolymer that gives a better balance of improved toughness without tradeoffs to other key performance properties and processibility.
FOAM EXTRUSION OF POLYSTYRENE WITH SUPERCRITICAL CARBON DIOXIDE IN A TWIN-SCREW EXTRUDER SYSTEM
The enhanced mixing of gas and polymer phases is important in all stages of the foam extrusion process. Much of the mixing in extrusion foam process is distributive, and prefers mixers which can divide and recombine melts at high rates and low energy. The twin-screw extruder provides the flexibility in screw elements design for better mixing. The effect of five different screw configurations on foaming characteristics of polystyrene (PS) with supercritical carbon dioxide (CO2) in a twin-screw extruder was investigated. It was found that with proper design of screw elements, it is possible to make foams with optimal foam density and cell morphology using twin-screw extruder system.
THE EFFECT OF MOLECULAR WEIGHT ON HEAT SEAL PROPERTY FOR HIGH DENSITY POLYETHYLENE FILM
The effect of molecular weight on heat seal properties for high-density polyethylene (HDPE) film was studied. HDPE compounded with 3 to 20 wt % higher molecular weight components was cast into film. Heat seal tests were carried out for the cast HDPE film. The heat bar temperature was controlled at 125 and 128 ?§C. The seal pressure was kept at 0.2 MPa constantly. The heat seal time for applying heat and pressure was varied from 0.5 to 2.0 sec. The molecular structure developed during the heat seal process was evaluated by differential scanning calorimetry (DSC) and wide-angle x-ray diffraction (WAXD) and relationships were drawn againstheat seal strength measured by T-peel test. Generally, by compounding higher molecular weight components, heat seal strength was decreased. However dosage of 3 to 10 wt % higher molecular weight components could shorten seal time to obtain sufficient heat seal strength at 128 ?§C heat seal temperature.
FILLING BALANCE OPTIMIZATION BY BEST GATE LOCATION
The quality of an injection molded part is strongly influenced by the filling balance of the mould cavity. This paper presents a method and the relevant software application to determine the best gate location for an injection molded part. The proposed optimization method automatically and iteratively calculates the gate position that maximizes the melt flows balance during the filling phase. The software is based on the Moldflow Plastics Insight®/Microsoft Visual Basic® interface and uses a non-linear optimization algorithm based on the Gauss-Newton and Conjugated Gradient techniques. The effectiveness of the developed method is demonstrated through some significant case studies.
THE HIGH PRESSURE RHEOLOGY OF POLYMER NANOCOMPOSITES CONTAINING SUPERCRITICAL CARBON DIOXIDE
Supercritical carbon dioxide has advantages of high solubility to the polymer and recovering easily by depressurizing, and it is expected to be use as a plasticizing agent. In this work, we studied on the effect of scCO2 on rheological properties of plastomer layered silicate nanocomposites. A rotational viscometer has been adapted to measure the viscosity of polymer under high temperature and pressure conditions. The rheological properties of Plastomer nanocomposites was performed at experimental conditions of various temperature and pressure. We observed that viscosity of polymer was dramatically reduced by CO2 addition.
LOW TEMPERATURE CURE KINETICS OF VINYL ESTER AND UNSATURATED POLYESTER/CARBON NANOFIBER NANOCOMPOSITES
Unsaturated polyester (UP) and vinyl ester (VE) resins are two of the most widely used thermoset resins in fiber reinforced composites due to their low cost and good processability. Adding nanoparticles like carbon nanofibers (CNFs) as a third phase into conventional composites results in hybrid nanocomposites with improved mechanical properties and multi-functionalities, and at the same time makes the curing reaction even more complex. In this paper, the effects of CNFs on the reaction kinetics of the two free radical polymerization systems are studied. VE/CNF kinetics is presented in more detail including interesting interactions between CNFs and curing ingredients in the system. Preliminary reaction kinetics data of UP/CNF is also presented.
VISUALIZATION STUDY ON THE FILLING PROCESS OF PS/SC-CO2 DURING MICROCELLULAR INJECTION MOLDING
Microcellular injection molding attracts more and more interests in industry because of its advantages, such as weight reduction, energy saving, cycle time reduction, etc.. In order to investigate the filling process of microcellular injection molding, a visual mold was developed in this work. The filling processes of polystyrene/carbon dioxide was observed and recorded using a digital camera, while the mold cavity pressure was measured by a sensor. The final bubble morphology was observed using scanning electron microscope. The experiment results showed that melt temperature and mold cavity pressure were two most prominent factors influencing bubble morphology.
STRUCTURE AND PRPERTIES OF MELT-SPUN PET/MWCNT NANOCOMPOSITE FIBERS
The structure and properties of polyethylene terephthalate (PET)/multi-wall carbon nanotube (MWCNT) fibers were investigated in this work. PET/MWCNT nanocomposite was obtained through melt mixing and CNT masterbatch dilution into desirable concentration. PET/CNT nanocomposite was then shaped to microfibers at different CNT concentrations and drawing conditions. The dispersion and distribution of CNT were optimized and the effect of processing condition on the morphology of nanocomposite was investigated by various microscopy techniques. Through the dispersion optimization, conductive fibers were obtained at 2% concentration of MWCNT. The study of crystalline structure of the fibers shows the role of CNT addition on enhancement of crystallinity in rod-like fibers; while in drawn fibers, it causes decrease in both the crystallinity and orientation during melt-spinning. Fiber production enhances the electrical conductivity along fiber axis. In addition, the increase in crystallinity by adding CNT shifts the mechanical properties to quite brittle behavior.
EFFECTS OF FREE SURFACE AND SUBSTRATE INTERACTIONS ON THE DISTRIBUTION OF GLASS TRANSITION TEMPERATURES IN NANOCONFINED POLYMERS
A fluorescence/multilayer technique was used to determine the distribution of glass transition temperatures (Tgs) in nanoconfined poly(methyl methacrylate) films. Poly(methyl methacrylate) exhibits an attraction to silica shown by an increase in Tg near the substrate. Perturbations in dynamics associated with Tg near a free surface lead to a Tg decrease. Both effects are shown to penetrate some tens of nanometers into a nanoconfined film. Effects of nanoconfinement on the transition between free-surface bulk and substrate Tg are explored with potential application to nanocomposite behavior.
EFFECTS OF FREE SURFACE AND SUBSTRATE INTERACTIONS ON THE DISTRIBUTION OF GLASS TRANSITION TEMPERATURES IN NANOCONFINED POLYMERS
A fluorescence/multilayer technique was used to determine the distribution of glass transition temperatures (Tgs) in nanoconfined poly(methyl methacrylate) films. Poly(methyl methacrylate) exhibits an attraction to silica, shown by an increase in Tg near the substrate. Perturbations in dynamics associated with Tg near a free surface lead to a Tg decrease. Both effects are shown to penetrate some tens of nanometers into a nanoconfined film. Effects of nanoconfinement on the transition between free-surface, bulk, and substrate Tg are explored, with potential application to nanocomposite behavior.
CHARACTERISATION OF DENSIFICATION TEMPERATURE IN ROTATIONAL MOULDING
The temperature at which densification ends for a range of blends comprising a metallocene catalysed medium density polyethylene (PE) in two different physical forms (powder and micropellets) were investigated using a novel data acquisition system (TP Picture??) developed by TotalPetrochemicals . The various blends were subsequentlyrotomoulded and test specimens prepared for mechanical analysis to establish the relationship between densification rate and bubble size / distribution on the part properties.The micropellets exhibited more rapid bubble removal times than powder.
EFFECT OF SURFACE MODIFIED MULTI-WALLED CARBON NANOTUBES ON THE LOW TEMPERATURE CURE KINETICS OF WIND BLADE EPOXY SYSTEM
The effect of multi-walled carbon nanotubes (MWNTs) on the curing kinetics of wind blade epoxy resin system was investigated. Isothermal differential scanning calorimetry technique was used to study the reaction kinetics. A comparison was made between the effect of pristine nanotubes and surface functionalized nanotubes on the epoxy polymerization kinetics. It was found that the curing reaction could be accelerated and resin conversion at room temperature could be increased using appropriate surface functionalization. This could find useful application in reducing the composite manufacturing times for large parts like wind blades.
EFFECT OF FORCED ASSEMBLY NANOLAYERING ON THE PHYSICAL AGING OF POLYSULFONE FILMS
The effect of layer thickness on the physical aging of nanolayered glassy polysulfone (PSF) against a rubbery random copolymer ethylene octene (EO) layer was investigated via forced assembly coextrusion. A post-extrusion thermal treatment above the Tg of polysulfone was developed to allow for a reset physical aging process. Physical aging of thermally reset polysulfone/ethylene-octene nanolayered films was performed and monitored through a thermal aging under elevated temperatures. The relationship of layer thickness to polysulfone physical aging was investigated through thermal analysis microscopy and positron annihilation spectroscopy.
EFFECTS OF NYLON6 NANOCOMPOSITES WITH NANOCLAY QUANTITY ON PART MOLDABILITY OF IN MOLD DECORATION MOLDING
Nylon6 nanocomposites (with2.0 wt% and 4.0 wt% nanoclay-montmorillonite) and two kinds of PC film with thickness of 0.125 mm and 0.175 mm combined varied ink formulas were used to investigate the effect of nanoclay quantity on ink washout of in mold decoration molding (square plate specimen with thickness of 2.0mm). It was found that Nylon6 nanocomposites with nanoclay quantity of 4.0wt% would increase 30% washout area than of 2.0wt% addition quantity. In addition, higher injection speed would increase shear stress leading to large ink washout area whereas higher melt temperature would decrease ink washout area.
MELT FLOW ANALYSIS OF ABS IN FUSED DEPOSITION MODELLING PROCESS
This paper presents a numerical study of melt flow behaviour of ABS plastic through the melt flow tube of the liquefier head of the Fused Deposition Modelling (FDM) rapid prototyping process using the finite element analysis. Main flow parameters including temperature, velocity and pressure drop have been investigated. Liquefier head of FDM machine has been modelled parametrically and the effects of physical modifications including nozzle angle variation on the melt flow parameters have been investigated accordingly. Results provide promising information on flow behaviour of new ABS based composites for processing in the FDM system to fabricate new products.
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